import org.postgresql.ds.PGSimpleDataSource;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Objects;

public class Main {

    public static void main(String[] args) throws SQLException {
        PGSimpleDataSource ds = new PGSimpleDataSource();
        ds.setServerName("db.dai.fmph.uniba.sk");
        ds.setPortNumber(5432);
        ds.setDatabaseName("playground");
        ds.setUser("horvath186@uniba.sk");
        ds.setPassword("dbPass1234");

        try (Connection c = ds.getConnection()){
            showEmployees(c, 5, 2);
            System.out.println(compare(c,
                    "SELECT employee_id FROM employees WHERE salary < 2000",
                    "SELECT employee_id FROM employees WHERE salary > 2000"));
        }
    }

    static void showEmployees(Connection c, int pageSize, int pageIndex) throws SQLException {
        try(Statement s = c.createStatement()) {
            //s.executeQuery("SELECT import_company()");

            String sql = "SELECT employee_id, first_name, last_name FROM employees LIMIT "
                    + pageSize + " OFFSET " + pageIndex * pageSize;


            try(ResultSet r = s.executeQuery(sql)) {
                while(r.next()) {
                    int employeeId = r.getInt(1);
                    String firstName = r.getString(2);
                    String lastName = r.getString(3);

                    System.out.println(employeeId + " " + firstName + " " + lastName);
                }
            }
        }
    }
    public static boolean compare(Connection c, String sql1, String sql2) throws SQLException {
        try (Statement s1 = c.createStatement()){
            try (Statement s2 = c.createStatement()) {
                try (ResultSet r1 = s1.executeQuery(sql1)) {
                    try (ResultSet r2 = s2.executeQuery(sql2)) {
                        while(r1.next() && r2.next()) {
                            String c1 = r1.getString(1);
                            String c2 = r2.getString(1);

                            boolean same = Objects.equals(c1, c2);

                            if (same == false) {
                                return false;
                            }
                        }
                    }
                }
            }
        }
        return true;
    }
}